On Thu, May 26, 2016 at 10:39:31PM +0200, Radim Krčmář wrote: > 2016-05-26 10:32+0300, kmeaw@xxxxxxxxxxxxxx: > > From: Dmitry Bilunov <kmeaw@xxxxxxxxxxxxxx> > > > > Intel CPUs having Turbo Boost feature implement an MSR to provide a > > control interface via rdmsr/wrmsr instructions. One could detect the > > presence of this feature by issuing one of these instructions and > > handling the #GP exception which is generated in case the referenced MSR > > is not implemented by the CPU. > > > > KVM's vCPU model behaves exactly as a real CPU in this case by injecting > > a fault when MSR_IA32_PERF_CTL is called (which KVM does not support). > > However, some operating systems use this register during an early boot > > stage in which their kernel is not capable of handling #GP correctly, > > causing #DP and finally a triple fault effectively resetting the vCPU. > > > > This patch implements a dummy handler for MSR_IA32_PERF_CTL to avoid the > > crashes. Most notably it fixes an issue with MacOS X 10.10 kernel. > > > > Signed-off-by: Dmitry Bilunov <kmeaw@xxxxxxxxxxxxxx> > > --- > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > @@ -2050,6 +2051,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > > case MSR_VM_HSAVE_PA: > > case MSR_AMD64_PATCH_LOADER: > > case MSR_AMD64_BU_CFG2: > > + case MSR_IA32_PERF_CTL: > > break; > > Does MacOS X write it too? After setting /sys/module/kvm/parameters/ignore_msrs, all I get in dmesg after firing up OS X is: vcpu0 ignored rdmsr: 0x199 So no, I don't think it would try to write it. HTH, --Gabriel -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
